BRYOZOA. 295 
Batostoma winchelli.] 
more or less separated by partially filled mesopores. The acanthopores also increase 
in size and distinctness but, being situated either in the interspaces or on the outer 
side of the zocecial walls, never encroach upon the zocecial cavities. In the axial 
region of vertical sections the tubes have irregularly undulating thin walls and no 
diaphragms. Nor are these structures developed except in the unusually narrow 
peripheral region, where from one to three have been observed in each tube. The 
mesopores are very short and provided with two or three thick diaphragms; or they 
may appear to be filled with solid tissue. ; 
The oval zocecial apertures, more slender growth, and absence of monticules 
are the most striking differences between the present species and b. montuosum. 
The zoarium is smaller, the branches more slender, and the peripheral region much 
narrower than in B. variwm. An undescribed variety of B. jamesi Nich. sp., occurring 
in the Utica horizon at Cincinnati, Ohio, corresponds more nearly than any of the 
known Minnesota species of the genus. 
Formation and locality—Moderately abundant in the Galena shales at St. Paul and near Cannon 
Falls, Minnesota. Also at Decorah, Iowa. A similar, perhaps identical, species occurs in the Trenton 
of central Kentucky. 
Mus. Reg. Nos. 7613, 8063. 
Batostoma wiNncHELLI Ulrich. 
PLATE XXVI, FIGS. 33-37; PLATE XXVII, FIGS. 1-6. 
Amplexopora winchelli ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sur. Minn., p. 91. 
Zoarium irregularly ramose; branches subcylindrical or a little compressed, 
varying in diameter from 4 to 10 mm., but in nine-tenths of the fragments seen from 
5to7 mm. In the typical and common form of the species monticules are wanting, 
nor are the clusters of apertures of larger size than the average, which sometimes 
take their place, ever a conspicuous feature. Occasionally they are rendered more 
distinct than usual by a thickening of the interspaces and an aggregation of the 
mesopores. In a variety that may be distinguished as nodosa, the surface is thrown 
up into more or less strongly marked monticules. Zocecial apertures rounded 
or subangular, rather irregularly arranged, ten to twelve in 3 mm.; walls moderately 
thick in most specimens, comparatively thin in young, very thick in worn old ones, 
ridge-shaped when perfect, and with acanthopore spines at nearly all angles of 
junction. Mesopores sparingly developed, never as numerous as the zoccia, occur- 
ring chiefly in small straggling clusters, their mouths open, of various sizes, some of 
them apparently developing into zoccia. 
